Photothermal imaging bundle system for estimating tissue oxygen saturation

Abstract

The objective of this study is to validate a method for the measurement of tissue oxygen saturation level via a thermal imaging bundle in-vitro and in-vivo. The method consists of a thermal imaging system and an algorithm which estimates the compound concentration according to the temperature rise of the tissue. A temperature rise is obtained by illuminating the tissue in the NIR range and is measured using a thermal camera and a coherent thermal imaging bundle for non-invasive transendoscopic use. The system was validated using agar phantoms of varying concentrations of Methylene Blue and ICG as well as blood samples. The algorithm estimated the Methylene Blue relative amount and the results were compared to the real relative amount. The calculated RMS of the error was 5.12%, a satisfying value for this stage. In the blood samples, for oxygenation levels higher than 50% the RMS of the error was 5.79%. Once the system was verified a portable system was built for clinical use, this system was also evaluated on agar phantoms and the RMS of the error was 10.64%. As a result of the encouraging experiments in-vivo, animal trials were performed. The oxygenation levels of mice were decreased and were estimated respectively using our system. The system determined a small decrease in the tissue oxygen saturation of the mice. These results verify the algorithm's and bundle's suitability for the use in a non-invasive system. They provide motivation for performing more complex in-vitro experiments and moving on to clinical trials.